1. Reflector Antennas Antenna and Microwave Laboratory In the name of God
Babol Noshirvani University of Technology, Iran
Reflector Antennas
Import video, voice + dipole 60cm

2. 1. Geometry:
Paraboloid
Sphere/Ellipsoid
Hyperboloid

3. Type 1 : Prime-Focus Antenna
2. Radiation Mechanism:
Type 1 : Prime-Focus Antenna
Main Reflector: Parabolic
Parabola has 2 valuable properties :
1) rays emanating from the focus are all reflected to parallel paths.
2) All paths from the focus to a plane transversal to the aperture at any distance, have the same length.
Constructive phase like array, when the reflector is large:physical optic
Constructive phase

4. Type 2 : Offset Reflector Antenna
Main Reflector: Parabolic

5. Type 3 : Cassegrain Antenna
Main Reflector: Parabolic
Subreflector: Hyperbolic

6. Type 4 : Gregorian Antenna
Main Reflector: Parabolic
Subreflector: Elliptic

7. Type 5 : Offset Cassegrain/Gregorian Antenna

8. Type 6 : ADE (Axially Displaced Ellipse) Antenna
Main Reflector: Parabolic
Subreflector: Elliptic

9. 3. Design Procedure:
However, Antenna Laboratory of Babol Noshirvani University of Technology Proposes a “Rule of Thumb Method”
So Let`s follow that

10. 3. Design Procedure: A) Illumination Taper Illumination loss
Spillover loss
Illumination taper (dB) =
illu loss / spillover loss
Ideal (uniform reflector) illumination
practical (non-uniform reflector) illumination

11. Step 1: illumination taper in Reflector
3. Design Procedure:
Different illumination taper values
Step 1: illumination taper in Reflector
Antenna should be somewhat
between 10db to 15db.
Step 2: Main dish diameter (D) is then calculated (in λ)

12. 3. Design Procedure: fp
Step 3: search the market for available Horn Antenna as the feed source. Remember that you can find only some standard pre-fixed antenna, not any size you like !
phi D
… find the HPBW of Horn in its datasheet.
Step 4: 1) set HPBW ≈ 2*phi
2) phi=Arctan[1/(2*(fp/D))]
3) fp is then calculated (in λ).
Step 5: check 0.25< fp/D <.65. if not, start again from step 1 with a different value.

13. 3. Design Procedure: fp
Step 5: now you can go to the mechanic to build your dish. However you need to give him the depth of the dish (x) rather than its focal point:
x= D^2/ (16*fp)
x is then calculated. x
phi D

14. HPBW(experimental)≈ 70*λ/D
4. Electromagnetic Properties:
Frequency Range: 300 MHz – 100 GHz
Bandwidth: 5%
Pattern: Pencil beam, dBi Gain, (1-10 deg HPBW)
Polarization: proportional to the Feed Antenna
In a fixed frequency, Larger Size of Dish yields to a greater gain.
HPBW(experimental)≈ 70*λ/D

15. 5. Applications: (visual review)
Green Bank Telescope which stands near Green Bank, West Virginia
The Very Large Array (VLA) at Socorro, New Mexico, United States for Radio Astronomy Applications
Space Satellite Antenna

16. 5. Applications: (visual review)
Reflector antenna used as radar in fighting ships
Air Surveillance Radar at the airport
IFF (identification of friend and foe)
Reflector Radar

17. 5. Applications: (visual review)
Arecibo Observatory is a radio telescope near city of Arecibo in Puerto Rico
Its spherical reflector has a 305m dish in diameter.
Surface is made of almost 40,000 perforated aluminum panels.
Its focal point is 150m above reflector.
These devices operate immersed in a liquid helium, to maintain a very low receiver temperature.
Arecibo system operates at frequencies from 10MHz (λ=30m) up to 50MHz (λ=6m).
1MW planetary radar transmitter located in a special room inside dome.
Contact

18. Now, Let`s get familiar with a brand new software: Antenna Magus

19. Go to CST and simulate a example And complete the work sheet

20. Reflector Antenna HPBW
Design Objectives for the Reflector Antenna set in Antenna Magus: f0
9.4 GHz
Feed Antenna HPBW
40 deg
Reflector Antenna HPBW
your desired (3-6 deg)

21. Reflector Antenna:

22. Reflector Antenna: Lg=31.89mm Hg=12.52mm Ha=64.5mm F=468.3mm D=330.3mm
Lf=154.8mm
Wg=25.04mm
Wa=90.3mm
S=468.3mm

23. Reflector Antenna:

24. Worksheet Please complete the work sheet to your example:
Frequency band : ………
The figure of antenna in CST : ………
The of size antenna in λ and in cm/mm : ………
S11 : ……… (set Z0=75 ohm)
Zin (Re and Im) in CST : ………
Surface Current (phase=0 deg) : ………
linear 3D Power Pattern in CST : ………
2D Power Pattern for theory & CST : ………
HPBW for theory & CST : ………